U.S. patent application number 12/808570 was filed with the patent office on 2011-01-06 for methods for producing composite elements based on foams based on isocyanate.
This patent application is currently assigned to BASE SE. Invention is credited to Roland Fabisiak, Rainer Hensiek, Peter Huntemann, Bernd Schaper, Lars Schoen, Maria Thomas, Ruediger Viereck.
Application Number | 20110003082 12/808570 |
Document ID | / |
Family ID | 40568642 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110003082 |
Kind Code |
A1 |
Schoen; Lars ; et
al. |
January 6, 2011 |
METHODS FOR PRODUCING COMPOSITE ELEMENTS BASED ON FOAMS BASED ON
ISOCYANATE
Abstract
The invention relates to a process for the production of
composites, composed of at least one outer layer b) and of an
isocyanate-based rigid foam a), where the outer layer b) is moved
continuously and the starting material for the isocyanate-based
rigid foam a) is applied to the outer layer b), which comprises
achieving the application of the liquid starting material for the
isocyanate-based rigid foam a) by means of at least one fixed tube
c) which has openings f) and which has been placed, with respect to
the outer layer b), so as to be parallel to the plane of the outer
layer and at right angles to the direction of movement.
Inventors: |
Schoen; Lars; (Nordhorn,
DE) ; Fabisiak; Roland; (Brockum, DE) ;
Hensiek; Rainer; (Melle, DE) ; Huntemann; Peter;
(Stemshorn, DE) ; Viereck; Ruediger; (Quernheim,
DE) ; Thomas; Maria; (Muehlen, DE) ; Schaper;
Bernd; (Diepholz, DE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
BASE SE
Ludwigshafen
DE
|
Family ID: |
40568642 |
Appl. No.: |
12/808570 |
Filed: |
December 15, 2008 |
PCT Filed: |
December 15, 2008 |
PCT NO: |
PCT/EP08/67517 |
371 Date: |
June 16, 2010 |
Current U.S.
Class: |
427/420 ;
118/314 |
Current CPC
Class: |
C08G 2110/0025 20210101;
B29C 44/461 20130101; B29C 31/047 20130101; B29C 31/042 20130101;
C09D 175/08 20130101 |
Class at
Publication: |
427/420 ;
118/314 |
International
Class: |
B05D 1/30 20060101
B05D001/30; B05C 5/00 20060101 B05C005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2007 |
EP |
07150059.9 |
Claims
1. A process for the production of composites, composed of at least
one outer layer b) and of an isocyanate-based rigid foam a), where
the outer layer b) is moved continuously and the starting material
for the isocyanate-based rigid foam a) is applied to the outer
layer b), which comprises achieving the application of the liquid
starting material for the isocyanate-based rigid foam a) by means
of at least one fixed tube c) which has openings f) and which has
been placed, with respect to the outer layer b), so as to be
parallel to the plane of the outer layer and at right angles to the
direction of movement.
2. The process according to claim 1, wherein at least two tubes c)
arranged alongside one another are used.
3. The process according to claim 2, wherein the arrangement of the
tubes c) having openings f) is such that they form a straight
line.
4. The process according to claim 2, wherein the tubes c) having
openings f) extend over at least 70% of the width of the outer
layer b), and at each of the edges of the outer layer b) there is a
region of equal width not covered by the tube.
5. The process according to claim 1, wherein the tubes c) having
openings f) extend over at least 80% of the width of the outer
layer b), and at each of the edges of the outer layer b) there is a
region of equal width not covered by the tube.
6. The process according to claim 1, wherein the tube c) having
openings f) has been placed at a height of from 5 to 30 cm above
the outer layer b).
7. The process according to claim 1, wherein the diameter of the
tube c) having openings f) is from 0.2 to 5 cm.
8. The process according to claim 1, wherein the internal diameter
of the tube c) having openings f) remains constant from the middle
to the ends of the tube.
9. The process according to claim 1, wherein the design of the tube
is such that, where the openings f) have been placed, the thickness
of the wall of the tube c) falls in the direction from the middle
of the tube c) to its ends.
10. The process according to claim 9, wherein the design of the
tube is such that, if a plurality of tubes c) is used, where the
openings f) have been placed, the thickness of the wall of the tube
c) has been designed so as to be equal in all of the tubes c).
11. The process according to claim 9, wherein the design of the
tube c) is such that, where the openings f) have been placed, the
thickness of the wall of the tube c) falls in the direction from
the site of the feed of the starting material for the
isocyanate-based rigid foam a) to the ends thereof in such a way
that the ratio of the length of the openings f) between the site of
the feed and the end of the tube c) is from 1.1 to 20 for each
tube.
12. The process according to claim 1, wherein, if only one tube c)
is used, the length of the openings f) falls from one external side
to the other, if the starting material for the isocyanate-based
rigid foam a) is fed from one side into the tube c).
13. The process according to claim 1, wherein the liquid starting
material for the isocyanate-based rigid foam a) is fed from the
middle of each tube c) having openings f).
14. The process according to claim 1, wherein the liquid starting
material for the isocyanate-based rigid foam a) is fed at the end
of each tube c) having openings f).
15. The process according to claim 1, wherein the diameter of the
openings f) is from 0.5 to 10 mm.
16. The process according to claim 1, wherein the distance between
the openings f) is from 5 to 200 mm.
17. The process according to claim 1, wherein the diameter of the
openings f) is the same over the entire length of the tube c).
18. The process according to claim 1, wherein the distance between
the openings f) is the same over the entire length of the tube
c).
19. The process according to claim 1, wherein the number of the
openings f) of the tube c) is even.
20. The process according to claim 1, wherein the number of the
openings f) of each tube c) is .gtoreq.2.
21. The process according to claim 1, wherein the mixing of the
components of the liquid starting material for the isocyanate-based
rigid foam a) takes place in mixing equipment which has connection
by way of feeds d) and e) to all of the tubes c) having openings
f).
22. The process according to claim 1, wherein each of the tubes c)
having openings f) has connection to precisely one feed d).
23. The process according to claim 1, wherein each of the tubes c)
having openings f) has connection to mixing equipment for the
mixing of the components of the liquid starting material for the
isocyanate-based rigid foam a).
24. The process according to claim 1, wherein the diameter of the
feeds d) is constant.
25. The process according to claim 1, wherein the diameter of the
feeds d) is from 4 to 30 mm.
26. The process according to claim 1, wherein the isocyanate-based
rigid foam a) comprises isocyanurate groups.
27. The process according to claim 1, wherein the viscosity of the
liquid starting material for the isocyanate-based rigid foam a) is
from 50 mPa*s to 2000 mPa*s at 25.degree. C.
28. The process according to claim 1, wherein the amount of the
liquid starting material applied to the outer layer b) for the
isocyanate-based rigid foam a) is from 2 kg/min to 100 kg/min.
29. An apparatus for the application of liquid reaction mixtures to
an outer layer b), where the outer layer b) is moved continuously
and the starting material for the isocyanate-based rigid foam a) is
applied to the outer layer b), wherein the application of the
liquid reaction mixture to the outer layer b) takes place by means
of at least two fixed tubes c) arranged alongside one another,
which have openings f) and which have been placed so as to be
parallel to the plane of the outer layers and at right angles to
the direction of movement of the outer layer b).
Description
[0001] The invention relates to a process for the production of
composite elements composed of at least one outer layer and of a
foam-forming reaction mixture, which is applied to the lower outer
layer by way of at least one fixed tube having openings.
[0002] The production of composite elements in particular composed
of metallic outer layers and of a core composed of isocyanate-based
foams, mostly of polyurethane (PU) foams or of polyisocyanurate
(PIR) foams, is widely practiced nowadays on continuously operating
twin-belt systems, these elements often also being called sandwich
elements. Elements for the design of facades on a very wide variety
of buildings are increasingly important, alongside sandwich
elements for cold-store insulation. The outer layers used here
comprise not only coated steel sheet but also stainless steel
sheet, copper sheet, or aluminum sheet. Particularly in the case of
facade elements, the surface structure of the boundary between the
foam and the outer layer is of decisive importance. For various
reasons, undesired air inclusions, known as vacuoles, often occur
between the lower outer layer and the isocyanate-based foam during
the production of the sandwich elements. In the facade-element
application, these air inclusions between metal sheet and foam can
cause the metal sheet to blister and make the facades unsightly,
particularly in the event of marked temperature changes and if the
color shades of the outer layer are dark.
[0003] Adhesive between the insulating foam and the lower outer
layer is also reduced. It is often the case that the lower outer
layer in sandwich elements has the poorest adhesion, determined by
the tensile test. Furthermore, the sheet metal underside is the
external side of the facade in the usual designs produced using
sandwich elements, and is therefore exposed to extreme conditions,
examples being temperature and suction effects. It is therefore
subject to greater stresses than the top side of the sandwich
element, and the result of this can be separation of the foam from
the metal sheet and likewise therefore blistering.
[0004] There is therefore a requirement to find a process which
lastingly minimizes vacuole formation at the surface of the
isocyanate-based rigid foams, or avoids this entirely, and which
functions even when the production process is subject to adverse
external circumstances. The process is intended to be capable of
continuous or batchwise use. Batchwise operation can, for example,
be used during start-up of the twin belt and for composite elements
produced by means of presses operating batchwise. Continuous use
takes place when twin-belt systems are used.
[0005] In the prior-art twin-belt process, the reaction mixture is
prepared by machinery using high- or low-pressure technology, and
is applied to the lower outer layer by means of oscillating rake
applicators. The rake here is stationary in the direction of
running of the belt, and oscillates across the width of the
element. A disadvantage of this method of application is that any
requirement for double-overlapping onto previously applied reaction
mixture applies fresh material leads to application of, thus giving
a mixture with different reaction states. The result of this
mixture is that the foam surface produced thereby does not rise
uniformly, and air is therefore included when the upper outer layer
is introduced. This disadvantage becomes more marked as the time
between application of the reaction mixture and the start of the
foam reaction becomes shorter. The speed of the continuously
operating twin belt is limited by the maximum possible oscillation
speed of the mixing head. Another disadvantage is that as the
amount of oscillation increases the amount of reaction mixture
applied in the edge region becomes greater and that applied in the
middle region of the outer layer becomes smaller.
[0006] In the alternative high-speed process, the reaction mixture
is applied to the lower outer layer by way of a multi-pronged
applicator, likewise including air bubbles in the reaction mixture
and likewise making it impossible to produce surfaces without
vacuoles. In addition, with this application method the reaction
mixture has to flow laterally across relatively large regions, the
result being production of relatively large vacuole zones on the
lower and upper outer layer, especially in the outermost regions,
before the individual strands from the multi-pronged applicator
coalesce. Furthermore, it is often possible to discern a groove, or
at least a defect in the foam, in the region where the strands from
the multi-pronged applicator coalesce.
[0007] In order to eliminate these shortcomings, DE 197 41 523
proposes that, after application of the liquid reaction mixture for
the rigid foam to the outer layer, air is blown onto the foam
mixture, which is still flowable. The intention of this is to
smooth the surface of the reaction mixture and to reduce the level
of air-bubble inclusion. A first disadvantage here is that the
blowing of air implies an additional step in the process. The blown
air can moreover produce areas of greater thickness of the reaction
mixture, and these likewise bring about an irregular surface.
[0008] It was then an object of the present invention to find an
application process for a reaction mixture of an isocyanate-based
rigid foam, in particular a PU system or PIR system, to a
horizontal metal sheet or to another flexible or rigid outer layer
which is continuously transported horizontally, this being the
usual method for the production of sandwich elements by a
continuously operating twin belt. The intention was that this lead
to a surface structure improved over the prior art for the foam on
the lower outer layer, and in particular to avoidance of vacuoles.
The process was moreover intended to lead to better adhesion
between outer layer and rigid foam. In particular, the intention
was that the surface of the applied foam be uniform. The process
was intended to be especially suitable for rapidly initiating
systems, and the intention here was to avoid the disadvantages
listed above for the multipronged applicator and for the
oscillating rake applicator.
[0009] Surprisingly, the object was achieved in that the reaction
mixture is applied to the lower outer layer b) by means of at least
one fixed tube c), hereinafter also termed rake applicator, which
has perforations and which has been placed, with respect to the
outer layer b), so as to be parallel and at right angles to the
direction of movement.
[0010] The invention therefore provides a process for the
production of composites, composed of at least one outer layer b)
and of an isocyanate-based rigid foam a), where the outer layer b)
is moved continuously and the starting material for the
isocyanate-based rigid foam a) is applied to the outer layer b),
which comprises achieving the application of the liquid starting
material for the isocyanate-based rigid foam a) by means of at
least one fixed tube c) which has openings f) and which has been
placed, with respect to the outer layer b), so as to be parallel to
the plane of the outer layer and at right angles to the direction
of movement.
[0011] The terms holes and perforations may be used as synonyms
hereinafter.
[0012] The invention further provides an apparatus for the
application of liquid reaction mixtures to an outer layer b), where
the outer layer b) is moved continuously and the starting material
for the isocyanate-based rigid foam a) is applied to the outer
layer b), which comprises achieving the application of the liquid
reaction mixture to the outer layer b) by means of at least two
fixed tubes c) arranged alongside one another, which have openings
f) and which have been placed so as to be parallel to the plane of
the outer layer and at right angles to the direction of movement of
the outer layer b).
[0013] In one preferred embodiment of the invention, the
arrangement of at least two tubes c) having openings f) is in
particular such that they form a straight line. It is preferable to
use from 2 to 4 tubes c), particularly preferably from 2 to 3, and
in particular 2.
[0014] The inventive rake applicator has, as described, a tubular
shape, with holes at the underside, distributed across the entire
length, and with the feed of the reaction mixture located either at
one end of the tubes c) or preferably in their middle. If a
plurality of tubes c) is used, the feed is preferably undertaken in
the same manner for all of the tubes c).
[0015] The length of the tubes c), or the length of the tubes c)
arranged alongside one another, can be the same as the width of the
outer layer b). It is preferable that the length of the tube c) is
smaller than the width of the outer layer b), in order to avoid
application of some of the reaction mixture alongside the outer
layer b). The arrangement of the rake applicator here is in the
middle above the outer layer b). The rake applicator preferably
covers at least 70% of the width of the outer layer b). If the
width of the outer layer b) is 1.20 m, as is usual for sandwich
elements, there would in this case be a width of 25 cm on each side
not covered by the rake applicator. It is preferable that the rake
applicator, or the rake applicators arranged alongside one another,
cover(s) at least 70% of the width of the outer layer b),
particularly preferably at least 80%, and in particular at least
95%.
[0016] The height of attachment of the rake with respect to the
lower outer layer b) is usually from 5 to 30 cm, preferably from 10
to 30 cm, and in particular from 15 to 25 cm.
[0017] The number of the openings f) along the rake is, as a
function of the length of the rake, at least 2, preferably at least
6, particularly preferably from 10 to 50, and in particular from 20
to 40. The number of the holes is preferably an even number.
[0018] The diameters of the openings f) are in the range from 0.5
to 10 mm, preferably from 1.0 mm to 4 mm. The distances between the
openings f) are preferably from 5 to 200 mm, particularly
preferably from 5 to 60 mm, and in particular from 10 to 30 mm.
This distance, and the diameter, are preferably the same over the
entire length of the tube c).
[0019] The internal diameter of the tube c) is from 0.2 to 5 cm,
preferably from 0.3 to 2.5 cm, and in particular from 0.2 to 2
cm.
[0020] In one particularly preferred embodiment, the length of the
openings f) differs over the length of the tube c). The length of
the openings f) means the distance which the mixture a) has to
travel from the interior of the tube c) until it is discharged from
the tube c). Various methods can be used for this purpose. Firstly,
the internal diameter of the tube c) can be altered. This is not
preferred, since components of this type are difficult to produce
and to clean.
[0021] It is preferable that the length of the openings f) is
altered in that a metal part is placed at the underside of the tube
c) in such a way that the length of the perforations is altered in
the desired manner. This measure in fact changes the wall thickness
of the tube c). The hole lengths, viewed from the site of the feed
of the starting material for the isocyanate-based rigid foam a) to
the end, do not decrease linearly, but decrease exponentially. The
usual manner of prolongation of the openings f) is such that the
length decreases from the feed of the mixture a) to the ends of the
tube c). That means that if the mixture a) is fed in the middle of
the tube c), the length of the openings f) falls in the direction
toward the ends. If the mixture a) is fed at the end of the tube c)
the length of the openings f) falls in the direction from the side
where the feed takes place to the other side.
[0022] The selection of the length of the openings f) here is
preferably such that the ratio of the length of the openings f)
from the end to the middle for each tube c) is from 1.1 to 10. The
ratio is particularly preferably from 2.5 to 10, in particular from
5 to 10.
[0023] If a plurality of tubes c) is used, the variation of the
length of the openings f) is designed to be equal for all of the
tubes c).
[0024] Each of the tubes c) having openings f) has connection to
mixing equipment for the mixing of the components of the liquid
starting material for the isocyanate-based rigid foam a). This is
usually achieved by means of a feed d) and e) situated
therebetween. The design of this feed is that of a tube, and if a
plurality of tubes c) is used, each tube has connection to the
feed. This can be achieved by using a tube from which in turn
connection tubes run out to the tubes c). FIG. 1 shows this type of
apparatus using two tubes c).
[0025] The diameter of the feeds d) is preferably constant. It is
preferably from 4 to 30 mm, particularly preferably from 6 to 22
mm.
[0026] The inventive process is suitable for any of the
isocyanate-based rigid foams, examples being polyurethane (PU)
foams and foams having urethane groups and having isocyanurate
groups, hereinafter also termed PU/PIR foams or simply PIR foams.
For many applications of the composites produced by the inventive
process, it is preferable that a PIR foam is used as
isocyanate-based rigid foam a).
[0027] The design of the inventive process is preferably such that
the amount of the liquid starting material applied to the outer
layer b) for the isocyanate-based rigid foam a) is from 2 kg/min to
100 kg/min, preferably from 8 kg/min to 60 kg/min.
[0028] The viscosity of the liquid starting material for the
isocyanate-based rigid foam a) is preferably from 50 mPa*s to 2000
mPa*s, particularly preferably from 100 mPa*s to 1000 mPa*s, at
25.degree. C.
[0029] The inventive process is particularly suitable for foams
where the cream time of the system is short. The cream time of the
systems used for the inventive process is preferably below 15 s,
with preference below 12 s, with particular preference below 10 s,
and in particular below 8 s, while the fiber time of the system is
from 20 to 60 s. Cream time is the time between the mixing of the
polyol component and the isocyanate component and the start of the
urethane reaction. The fiber time is the time from the mixing of
the starting components of the foams to the juncture at which the
reaction product becomes non-flowable. The fiber time is adapted
appropriately as a function of the thickness of the element
produced, and also the speed of the twin belt.
[0030] In one particular embodiment of the inventive process, an
adhesion promoter can be applied between the outer layer b) and the
isocyanate-based rigid foam a). The adhesion promoter used can
comprise the adhesion promoters known from the prior art.
Polyurethanes are in particular used, and it is possible here to
use either reactive single-component systems or reactive
two-component systems.
[0031] The adhesion promoter is applied in front of the tube c)
having perforations, in the direction of movement of the outer
layer b). The selection of the distance between application of the
adhesion promoter and application of the starting components for
the isocyanate-based rigid foam a) here is to be such that the
adhesion promoter has not entirely completed its reaction before
application of the starting components for the isocyanate-based
rigid foam a).
[0032] The adhesion promoter can be applied to the outer layer b)
by known processes, such as spraying. It is preferable that the
adhesion promoter has been applied to the outer layer b) by means
of a rotating flat disk which has been placed horizontally or with
a slight deviation from the horizontal of up to 15.degree., and
preferably in a manner such that it is parallel to the outer layer
b). The disk can be, in the simplest case, circular, or elliptical,
and flat. The design of the disk is preferably serrated or
star-shaped, and the points of the star here can have an upward
curve.
[0033] The disk can be completely flat, or can have upward
curvature or angling at the edge. It is preferable to use a disk
whose edges have upward curvature or angling. Holes are introduced
into the angled portion, in order to ensure discharge of the
adhesion promoter. The diameter and number of the holes are
appropriately adjusted to one another, in order to permit
application of the adhesion promoter in finely dispersed form to
the underlying outer layer b) with maximum uniformity, and to allow
discharge of all of the material applied to the disk, and to
minimize the maintenance cost of the disk.
[0034] In one embodiment, the design of the disk is of cascade
type. The arrangement of the cascades here rises from the axis of
rotation outward. At the transitions from one cascade to the
adjacent cascade, there can be holes placed within the disk, so
that a portion of the adhesion promoter can be discharged at these
cascade transitions onto the lower outer layer b). This type of
disk designed in the manner of a cascade provides particularly
uniform application of the adhesion promoter to the outer layer b)
situated thereunder. The application of the adhesion promoter to
the disk takes place at minimum distance from the axis of rotation.
Surprisingly, it has been found here that the adhesion promoter is
particularly uniformly distributed onto the lower outer layer b) if
the application point of the adhesion promoter is exactly prior to
or behind the axis of rotation, in parallel with the direction of
production.
[0035] The diameter of the disk is, as a function of the width of
the outer layer b), from 0.05 to 0.3 m, preferably from 0.1 to 0.25
m, particularly preferably from 0.12 to 0.22 m, based on the long
side. Its height of attachment above the outer layer b) to which
the liquid is to be applied is from 0.02 to 0.2 m, preferably from
0.03 to 0.18 m, particularly preferably from 0.03 to 0.15 m.
[0036] A disk having from 2 to 4 cascades, preferably from 2 to 3,
particularly preferably 2, can be used.
[0037] This type of application apparatus for the adhesion promoter
is described by way of example in WO 2006/029786.
[0038] The inventive process and the apparatus described are
particularly suitable for systems using physical blowing agents, in
particular pentanes. The inventive process is moreover preferred
for the production of composite elements with rigid outer
layers.
[0039] The outer layer b) used can comprise flexible or rigid,
preferably rigid, outer layers, examples being gypsum plasterboard,
glass tile, aluminum foils, aluminum sheet, copper sheet, or steel
sheet, preferably aluminum foils, or aluminum sheet or steel sheet,
particularly preferably steel sheet. The steel sheet can be coated
or uncoated sheet. The steel sheet can be pretreated, for example
using corona treatment, arc treatment, plasma treatment, or other
conventional methods.
[0040] The outer layer b) is preferably transported at a constant
speed of from 1 to 60 m/min, preferably from 2 to 150 m/min,
particularly preferably from 2.5 to 30 m/min, and in particular
from 2.5 to 20 m/min. The outer layer b) here is in a horizontal
position at least from the application of the foam system b)
onward, and preferably during the entire period from the
application of the adhesion promoter.
[0041] In the inventive process, when using sheet and foils as
outer layers, the outer layers are unwound in succession from a
roll, if appropriate profiled, and heated, and if appropriate
pretreated, in order to increase ease of application of
polyurethane foam, and the adhesion promoter is optionally applied,
the starting material for the isocyanate-based rigid foam a) is
applied by means of the inventive stationary rake, and hardened in
the twin-belt system, and the product is finally cut to the desired
length.
[0042] The isocyanate-based rigid foams a) used for the inventive
process are produced in a conventional and known manner, via
reaction of polyisocyanates with compounds having at least two
hydrogen atoms reactive with isocyanate groups, in the presence of
blowing agents, catalysts, and conventional auxiliaries and/or
additives. Details of the starting materials used are as
follows.
[0043] Organic polyisocyanates that can be used are any of the
known organic di- and polyisocyanates, preferably aromatic
polyfunctional isocyanates.
[0044] Individual examples which may be mentioned are tolylene 2,4-
and 2,6-diisocyanate (TDI) and the corresponding isomer mixtures,
diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate (MDI) and the
corresponding isomer mixtures, mixtures composed of diphenylmethane
4,4'- and 2,4'-diisocyanates, polyphenyl polymethylene
polyisocyanates, mixtures composed of diphenylmethane 4,4'-, 2,4'-
and 2,2'-diisocyanates and of polyphenyl polymethylene
polyisocyanates (crude MDI) and mixtures composed of crude MDI and
of tolylene diisocyanates. The organic di- and polyisocyanates may
be used individually or in the form of mixtures.
[0045] Use is also often made of what are known as modified
polyfunctional isocyanates, i.e. products obtained via chemical
reaction of organic di- and/or polyisocyanates. By way of example,
mention may be made of di- and/or polyisocyanates containing
uretdione groups, carbamate groups, isocyanurate groups,
carbodiimide groups, allophanate groups and/or urethane groups. The
modified polyisocyanates may, if appropriate, be mixed with one
another or with unmodified organic polyisocyanates, such as
diphenylmethane 2,4'- or 4,4'-diisocyanate, crude MDI, or tolylene
2,4- and/or 2,6-diisocyanate.
[0046] Use may also be made here of reaction products of
polyfunctional isocyanates with polyhydric polyols, or else of
mixtures of these with other di- and polyisocyanates.
[0047] An organic polyisocyanate which has proven particularly
successful is crude MDI, in particular with NCO content of from 29
to 33% by weight and a viscosity at 25.degree. C. in the range from
150 to 1000 mPas.
[0048] Compounds which may be used and which have at least two
hydrogen atoms reactive toward isocyanate groups are those which
bear at least two reactive groups selected from OH groups, SH
groups, NH groups, NH.sub.2 groups, and acidic CH groups,
preferably OH groups, and in particular polyether alcohols and/or
polyester alcohols whose OH numbers are in the range from 25 to 800
mg KOH/g.
[0049] The polyester alcohols used are mostly prepared via
condensation of polyhydric alcohols, preferably diols, having from
2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms, with
polybasic carboxylic acids having from 2 to 12 carbon atoms, e.g.
succinic acid, glutaric acid, adipic acid, suberic acid, azelaic
acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric
acid, or preferably phthalic acid, isophthalic acid, terephthalic
acid, or the isomeric naphthalenedicarboxylic acids.
[0050] The polyesterols used mostly have a functionality of from
1.5 to 4.
[0051] Polyether polyols particularly used are those prepared by
known processes, e.g. via anionic polymerization of alkylene oxides
onto H-functional starter substances in the presence of catalysts,
preferably alkali metal hydroxides or double-metal-cyanide
catalysts (DMC catalysts).
[0052] Alkylene oxides used are mostly ethylene oxide or propylene
oxide, or else tetrahydrofuran, various butylene oxides, or styrene
oxide, and preferably pure propylene 1,2-oxide. The alkylene oxides
can be used alone, in alternating succession, or in the form of a
mixture.
[0053] Starter substances particularly used are compounds having at
least 2, preferably from 2 to 8, hydroxy groups or having at least
two primary amino groups in the molecule.
[0054] Starter substances used and having at least 2, preferably
from 2 to 8, hydroxy groups in the molecule are preferably
trimethylolpropane, glycerol, pentaerythritol, sugar compounds,
such as glucose, sorbitol, mannitol, and sucrose, polyhydric
phenols, resols, e.g. oligomeric condensates composed of phenol and
formaldehyde, and Mannich condensates composed of phenols, of
formaldehyde, and of dialkanolamines, and also melamine.
[0055] Starter substances used and having at least two primary
amino groups in the molecule are preferably aromatic di- and/or
polyamines, such as phenylenediamines, 2,3-, 2,4-, 3,4-, and
2,6-tolylenediamine, and 4,4'-, 2,4'-, and
2,2'-diaminodiphenylmethane, and also aliphatic di- and polyamines,
such as ethylenediamine.
[0056] The preferred functionality of the polyether polyols is from
2 to 8 and their preferred hydroxy numbers are from 25 to 800 mg
KOH/g, in particular from 150 to 570 mg KOH/g.
[0057] Other compounds having at least two hydrogen atoms reactive
toward isocyanate are crosslinking agents and chain extenders which
may be used concomitantly, if appropriate. Addition of difunctional
chain extenders, trifunctional or higher-functionality crosslinking
agents, or else, if appropriate, mixtures of these can prove
advantageous for modification of mechanical properties. Chain
extenders and/or crosslinking agents preferably used are
alkanolamines and in particular diols and/or triols with molecular
weights below 400, preferably from 60 to 300.
[0058] The amount advantageously used of chain extenders,
crosslinking agents, or mixtures of these is from 1 to 20% by
weight, preferably from 2 to 5% by weight, based on the polyol
component.
[0059] The rigid foams are usually produced in the presence of
blowing agents, catalysts, flame retardants, and cell stabilizers,
and, if necessary, of other auxiliaries and/or additives.
[0060] Blowing agents which can be used are chemical blowing
agents, such as water and/or formic acid, these reacting with
isocyanate groups with elimination of carbon dioxide and,
respectively, carbon dioxide and carbon monoxide. The compounds
known as physical blowing agents can preferably also be used in
combination with water or preferably instead of water. These are
compounds inert with respect to the starting components, mostly
liquid at room temperature, and evaporating under the conditions of
the urethane reaction. The boiling point of these compounds is
preferably below 50.degree. C. Among the physical blowing agents
are also compounds which are gaseous at room temperature and which
are introduced or dissolved into the starting components under
pressure, examples being carbon dioxide, low-boiling alkanes, and
fluoroalkanes.
[0061] The blowing agents are mostly selected from the group
consisting of alkanes, formic acid and/or cycloalkanes having at
least 4 carbon atoms, dialkyl ethers, esters, ketones, acetals,
fluoroalkanes having from 1 to 8 carbon atoms, and
tetraalkylsilanes having from 1 to 3 carbon atoms in the alkyl
chain, in particular tetramethylsilane.
[0062] Examples which may be mentioned are propane, n-butane,
isobutane, cyclobutane, n-pentane, isopentane, cyclopentane,
cyclohexane, dimethyl ether, methyl ethyl ether, methyl butyl
ether, methyl formate, acetone, and also fluoroalkanes which can be
degraded in the troposphere and therefore do not damage the ozone
layer, e.g. trifluoromethane, difluoromethane,
1,1,1,3,3-pentafluorobutane, 1,1,1,3,3-pentafluoropropane,
1,1,1,2-tetrafluoroethane, difluoroethane, and heptafluoropropane.
The physical blowing agents mentioned may be used alone or in any
desired combinations with one another.
[0063] A mixture composed of formic acid, water, and pentane is
particularly preferred as blowing agent mixture.
[0064] The usual amount used of the blowing agent component is from
1 to 45% by weight, preferably from 1 to 30% by weight,
particularly preferably from 1.5 to 20% by weight, and in
particular from 2 to 15% by weight, based on the total weight of
the following components: polyol, blowing agent, catalyst system,
and any foam stabilizers, flame retardants, and other
additives.
[0065] The polyurethane foams or polyisocyanurate foams usually
comprise flame retardants. It is preferable to use bromine-free
flame retardants. Flame retardants comprising phosphorus atoms are
particularly preferred, and use is particularly made of
trischloroisopropyl phosphate, diethyl ethanephosphonate, triethyl
phosphate, and/or diphenyl cresyl phosphate.
[0066] Catalysts used in particular comprise compounds which
markedly accelerate the reaction of the isocyanate groups with the
groups reactive with isocyanate groups. Examples of these catalysts
are basic amines, e.g. secondary aliphatic amines, imidazoles,
amidines, and also alkanolamines, Lewis acids, or organometallic
compounds, in particular those based on tin. Catalyst systems
composed of a mixture of various catalysts can also be used.
[0067] If isocyanurate groups are to be incorporated in the rigid
foam, specific catalysts are needed. Isocyanurate catalysts usually
used are metal carboxylates, in particular potassium acetate and
its solutions. The catalysts may be used alone or in any desired
mixture with one another, as required.
[0068] Auxiliaries and/or additives which may be used are
substances known per se for this purpose, e.g. surfactants, foam
stabilizers, cell regulators, fillers, pigments, dyes,
antioxidants, hydrolysis stabilizers, antistatic agents,
fungistatic agents, and bacteriostatic agents.
[0069] Further details concerning the starting materials used for
carrying out the inventive process, blowing agents, catalysts, and
also auxiliaries and/or additives are found by way of example in
Kunststoffhandbuch [Plastics Handbook], volume 7, "Polyurethane"
["Polyurethanes"] Carl-Hanser-Verlag Munich, 1st edition, 1966, 2nd
edition, 1983, and 3rd edition, 1993.
[0070] To produce the rigid isocyanate-based foams a) the
polyisocyanates and the compounds having at least two hydrogen
atoms reactive toward isocyanate groups are reacted in amounts such
that the isocyanate index for the polyurethane foams is in the
range from 100 to 220, preferably from 115 to 180.
[0071] The index that can be used for operations in the production
of polyisocyanurate foams can also be >180, generally from 180
to 700, preferably from 200 to 550, particularly preferably from
250 to 500, and in particular from 270 to 400.
[0072] The rigid polyurethane foams can be produced batchwise or
continuously with the aid of known mixing apparatuses. Known mixing
apparatuses can be used to mix the starting components.
[0073] The inventive rigid isocyanate-based foams a) are usually
produced by the two-component process. In this process, the
compounds having at least two hydrogen atoms reactive toward
isocyanate groups are mixed with the blowing agents, with the
catalysts, and also with the other auxiliaries and/or additives to
give what is known as a polyol component, and this is reacted with
the polyisocyanates or mixtures composed of the polyisocyanates
and, if appropriate, blowing agents, also termed the isocyanate
component.
[0074] The starting components are usually mixed at a temperature
of from 15 to 35.degree. C., preferably from 20 to 30.degree. C.
The reaction mixture may be mixed using high- or low-pressure feed
machinery.
[0075] The density of the rigid foams produced is preferably from
10 to 400 kg/m.sup.3, preferably from 20 to 200 kg/m.sup.3, in
particular from 30 to 100 kg/m.sup.3.
[0076] The thickness of the composite elements is usually in the
range from 5 to 250 mm.
[0077] FIG. 1 shows the inventive apparatus using two tubes c).
[0078] A more detailed description of the invention will be given
in the examples below.
EXAMPLES
A) Constitution of a PU System
Polyol Component (A Component)
[0079] 44 parts of polyetherol 1 composed of propylene oxide and of
an aminic starter, functionality 4, hydroxy number 400 mg KOH/g
[0080] 26 parts of polyetherol 2 composed of propylene oxide and
saccharose as starter, OH number 400 mg KOH/g [0081] 5 parts of
polyetherol 3 composed of propylene oxide and trimethylolpropane as
starter, OH number 200 mg KOH/g [0082] 20 parts of flame retardant
1: trischloroisopropyl phosphate, TCPP [0083] 2 parts of
silicone-containing stabilizer [0084] 2 parts of catalyst 1:
amine-containing PU catalyst [0085] 1 part of catalyst 2:
amine-containing blowing catalyst [0086] Blowing agent 1: n-pentane
[0087] Blowing agent 2: water [0088] Blowing agent 3: 85% strength
aqueous formic acid
Isocyanate Component (B Component)
[0089] Lupranat M50 isocyanate: polymeric MDI (BASF AG), NCO
content: 31%, viscosity: 500 mPas at 25.degree. C.
[0090] A component, B component, and blowing agent were reacted in
ratios such that the index was in the region of 130 and the
envelope density achieved was 39 g/l.
B) Constitution of a PIR System
Polyol Component (A Component)
[0091] 66 parts of polyesterol 1 composed of phthalic anhydride,
diethylene glycol, and oleic acid, functionality: 1.8, hydroxy
number: 200 mg KOH/g [0092] 30 parts of flame retardant 1:
trischloroisopropyl phosphate, TCPP [0093] 1.5 parts of stabilizer
1, silicone-containing stabilizer [0094] 1.5 parts of catalyst 1,
PIR catalyst, salt of a carboxylic acid [0095] 1 part of catalyst
2, amine-containing PU catalyst [0096] Blowing agent 1: n-pentane
[0097] Blowing agent 2: water [0098] Blowing agent 3: 85% strength
aqueous formic acid
Isocyanate Component (B Component)
[0099] Lupranat M50 isocyanate: polymeric MDI (BASF AG), NCO
content: 31%, viscosity: 500 mPas at 25.degree. C.
[0100] The polyol component and the isocyanate component, and also
the blowing agent, were mixed with one another in ratios such that
the index was in the region of 350 and the envelope density
achieved was 43 g/l.
[0101] The polyurethane system and, respectively, polyisocyanurate
system a) was applied in succession by means of an oscillating rake
applicator and of a stationary rake applicator, composed of two
equal-length tubes c) arranged in a row.
[0102] The dimensions of the oscillating rake applicator were 25
cm.times.1.5 cm, and it had 41 holes with diameter 1.6 mm and with
a distance of 5 mm between the holes, and it oscillated with a
speed of 0.7 m/s across a distance of 1.0 m.
[0103] The dimensions of the stationary rake were 95 cm.times.15
cm, and it had 24 holes with diameter 2.8 mm and with a distance of
40 mm between the holes. The lengths of the holes of the openings
f) for each of the two tubes c) rose exponentially from the end to
the middle, beginning from 3 mm, as far as 19 mm.
[0104] The application rate for both rake systems was 25.1
kg/min.
[0105] The metallic outer layer was not corona-treated. The width
of the twin belt was 1.2 m and it was advanced at a constant speed
of 5.0 m/min. The temperature of the metal sheet was 37.degree. C.,
and that of the twin belt was set to 40.degree. C. (PU) and,
respectively, 60.degree. C. (PIR). The thickness of the sandwich
element was 100 mm.
[0106] After hardening of the system, test specimens of dimensions
100.times.100.times.5 mm were removed by sawing, and the adhesion
of the foam to the outer layer was determined to DIN EN ISO
527-1/DIN 53292.
[0107] The frequency of surface defects was determined
quantitatively by an optical method. For this, a plane was
introduced into a foam specimen at a distance of one millimeter
from the lower outer layer, i.e. from the outer layer on which the
polyurethane reaction solution has been applied in the twin-belt
process, and material above the plane was removed. The resultant
foam surface was illuminated with an aperture angle of 5.degree.,
and the area covered by shadow due to surface defect was calculated
as a ratio of the total surface area. For this, the illuminated
foam surface was photographed, and the foam images were then
digitized. The integrated area of the black regions of the
digitized images was calculated as a ratio to the total area of the
images, thus providing a measure of the frequency of surface
defects. An additional qualitative assessment of surface quality
was made on the foams, the outer layer being removed from a foam
specimen measuring 1 m.times.2 m and the surface being assessed
visually.
[0108] The various tests using different rigid foam systems with
oscillating and stationary rake applicator are compared in table
1.
TABLE-US-00001 TABLE 1 Experimental parameters and results.
Uniformity of application across the surface of the outer layer is
assessed here. Compressive Tensile Compressive modulus of Tensile
modulus of Number of Example Foam Rake strength elasticity strength
elasticity vacuoles/surface No. system system [N/mm.sup.2]
[N/mm.sup.2] [N/mm.sup.2] [N/mm.sup.2] Pattern defects 1 (C) PU
oscill. 0.14 2.7 0.10 4.1 Grooved 10% pattern 2 PU stationary 0.18
3.4 0.14 4.5 Flat, no 2% pattern 3 (C) PIR oscill. 0.13 3.1 0.10
3.9 Grooved 12% pattern 4 PIR stationary 0.18 4.2 0.17 5.5 Flat, no
1% pattern C = comparative example
[0109] The results in table 1 show that the frequency of formation
of surface defects at the boundary with the metallic outer layers
is markedly reduced, in comparison with the prior art, through use
of the inventive stationary rake applicator, and that the
mechanical properties of the foam are improved, as also is the
adhesion between rigid foam and outer layer.
* * * * *